Magnetic speedometer



Jan- 3, 1939 A. w. L E FEVRE ET A1. 2,142,248

MAGNETI C SPEEDOMETER Filed Jan. 3l, 1936 Patented Jan.l 3, 1939 UNITEDSTATES PATENT OFFICE 2,142,248 MAGNETIC sPEEDoMETE'n Application January31, 1936, Serial No. 61,734

4 Claims.

This invention relates to magnetic speedometers, and its purpose is toprovide an instrument of this type which shall be extremely inexpensiveto manufacture so as to be available for use on inexpensive vehicles.such as bicycles or childrens toy automobiles and velocipedes. Itconsists of various features and elements of construction in combinationas herein shown and described and as indicated by the claims.

In the drawing:

Figure 1 is a face view of an instrument embodying this invention. 1

Figure 2 is a side elevation of the same.

Figure 3 is a transverse section on an enlarged scale, taken asindicated at line 3--3 on Figure 1.

Figure 4 is a detail section taken as indicated at line l--l on Figure3, but on the same scale as Figure 2.

Figure 5 is a detail section taken as indicated at line 5-5 on Figure 3.

In an instrument of this character the essential elements are a rotatingmagnet driven by the wheel or shaft whose speed is to be measured, and aspring-biased drag element, usually ,25 in the form of a disk or cup oinon-magnetic metal, such as aluminum, adapted to be drawn from a zeroposition to a speed-registering position corresponding to the speed ofrevolution of the magnetic element. Associated with the drag element, ofcourse, is a suitable dial and an index member, such as a pointer.

In the drawing the magnet, l, is shown as annular in form, with theusual gap at I between its poles, and it is carried by a stamped metalcore or mounting, 2, which is in the form of a disk, doubled back uponitself at 2 in the vicinity of its periphery, and then bent at rightangles to form an annular flange, 2b, fitting snugly into the annularmagnet, l, and peened over at 2 for permanently securing the magnetagainst the base flange formed by the doubling of the material at 2*.I'his core member, 2, is xed to a drive shaft, 3, whose inner end isreduced to .form a shoulder against which the member, 2, is seated, andupon which it is secured by peening over the extreme end portion of theshaft at 3. 'I'he other end of the shaft is axially bored at 3b, and aportion of it is then constructed at 3 to form a squared socket intowhich the squared end,

l", of any suitable exible drive shaft, l, is disengageably fitted. Theshaft, 3, is journaled in a hollow stem or bushing, 5, projectingaxially from the rear of the case, 6, and permanently secured in acentral opening in the case by the peening method, as seen at 6. Theouter end of the shaft,

3, carries a collar, 3d, permanently held thereon and serving as a stopshoulder with a thrust Washer, 3, interposed for running engagement withthe shoulder, 3, in the bearing stem, 5..

The inner end of the shaft, 3, is counter-bored 5 at 3f, and formed witha central bearing recess, 3g, for the inner end of the spindle, 1, whichcarries the drag element in the form of anlaluminum cup, 8. Intermediateits ends the spindle, 1, is knurled or uted at 1 for interlockingengage- 10 ment with a hub flange, 8, formed at the center of the cup,8. The annular flange, 8b, of the cup encompasses the magnet, i, withclearance and fits rotatively within the annular Wall, 6b, whichimmediately joins the back wall of the case, 6, l5 and which ispreferably made of magnetic metal, such as steel, so as to serve as afield member for the magnet, l, tending to concentrate the flux in theannular gap between said magnet and the wall, 6b, thus drawing itthrough the skirt or I) ange, 8b, of the drag element, 8.

The chamber formed within the annular wall, 6b, of the case and servingto house the magnet, I, and the drag element, 8, is further defined by atransverse partition, 9, preferably of magnetic 25 material, so that itshall also serve as a field plate tending to draw a portion of themagnetic flux through the at circular portion of the member, 8. Thispartition, 9, is seated against a transverse shoulder, 6, of the case,which is disposed between 30 the annular wall, 6b, and a slightly largerannular portion, 6d, into which the projecting peripheral lugs, 9B, ofthe plate, 9, fit tightly when the plate is forced into position forfrictional securement. Just beyond the shoulder, 6, the material is 35crimped into bead, 6, to avoid a llet in the angle between thetransverse portion, 6, and the annular portion, 6d, and thus ensure firmseating of the plate, 9, against the shoulder, 6. 'Ihe central portionof the partition plate, 9, is cut away 40 at 9b, but so as to leave aprojecting stop iinger,

9, to engage the upstanding lug, 8, of the drag element, 8, at itsnormal zero position, or in the event that it should be turned through anearly complete revolution. The biasing hair-spring, 45 I0, is anchoredat its inner end between a pair of collars, I l forced on the spindle,1, while the outer end of the spring is gripped between three upstandingngers, 9d, extending from the plane of the plate, 9, and formedintegrally therewith. It 50 is a comparatively simple matter inassembling the instrument, to draw the end of the spring into the spaceformed between one pair of these iingers, 9d, and the third nger offsettherefrom, and then to pinch the fingers together to grip this 56 2auaua end of the spring when it has been tensioned Just sumciently tobring the lus. l, against the stop, 9.

Beyond the annular portion, l, of the casing the material extendsoutwardly in a i'lat annular 5 portion, I. to which the dial plate, l2,is aiiixed bylugs, l2, extending through radial slots. lf,

and clinched over against the back of the part,

, 0. The dial plate has a central aperture which serves as a secondbearing for the spindle, 1, and the projecting end oi' the spindlecarries an indicating hand or needle, Il, frictionally held thereto byits hub. A cover glass, i4, spaced from the dial plate, i2, by a ring,I5, of paper, fiber or other suitable cushioning material is secured bya bezel ring, I8, whose marginal iiange,

It., is crimped inwardly at several points, as indicated at I lb, justback of the fiat annular a portion, I', of the casing. To preventclouding of the under surface of the cover glass by condensation ofmoisture the dial plate, I2, and the portion, 0, of the casing a" formedwith registering breather holes, I1.

Thus it will be seen that the assembly of the instrument is accomplishedentirely without screws or rivets, but by simple upsetting or deformingoperations by which the various parts are permanently and firmly securedtogether. 'I'his keeps the cost of manufacture down to a figurecommensurate with the -use for which the instrument is intended without,in any Wise, endangering the certainty of its satisfactory operation.

While there is shown and described herein certain specific structureembodying the invention, it will be manifest to those skilled in the artthat various modifications and re-arrangements of the parts may be madewithout departing from the spirit and the scope of the invention, andthat the same is not limited to the particular form herein shown anddescribed, except in so far as indicated by the appended claims.

We claim:

l. In a magnetic speedometer of the type which includes a shaft, anannular magnet carried thereby, speed-responsive means associatedtherewith including a nonmagnetic drag cup whose annular wallencompasses the magnet, a dial plate and a cover glass; a case ofmagnetic metal having a central annular portion disposed adjacent themagnet and closely encompassing said annular wall oi' the drag cup toserve as a field member for the magnet, a bearing sleeve for the shaftfixed axially to said central portion of the case, the speedometerincluding also a spindle for said drag cup having a bearing for itsinner end in the end of the shaft, said case including an outwardlyfiaring flange extending from its said central portion, the dial platebeing seated on said flange and providing a second bearing at its centerfor said spindle, said flange of the case having peripheral notches, andsaid dial plate being secured to the case by means of lugs clinched overthe flange through said notches to retain it.

2. In a magnetic speedometer of the type which includes a shaft, anannular magnet carried thereby, speed-responsive means associatedtherewith including a non-magnetic drag cup whose annular wallencompasses the magnet. a field plate extending over the drag cup, adial plate, a spindle for the drag cup journaled in the dial plate andcarrying a pointer positioned to swing over the dial plate, and a coverglass over the pointer with a spacer interposed between the dial plateand the cover glass; a case for said elements comprising a shell ofmagnetic metal having a central, annular portion extending adjacent themagnet and closely encompassing the annular wall of the drag cup toserve as a field member` for the magnet, with a central web at one endof said annular portion of the case, and a bearing for the shaft securedto said web, the case being of stepped formation including a nrst `stepextending radially outward from the other end of said annular portionfor seating the field plate, and a second step extending farther outwardfor seating the dial plate, together with a bezel ring embracing thecover glass and said second step, with the spacer interposed.

3. In a magnetic speedometer of the type which includes a shaft, anannular magnet carried thereby, speed-responsive means associatedtherewith including a non-magnetic drag cup whose annular wallencompasses the magnet, a dial plate and a cover glass: a case having acentral 'annular portion, a bearing sleeve for the shaft fixed axiallyto said central portion of the case, the speedometer including also aspindle for said drag cup having a bearing for its inner end in the endof the shaft, said case including an outwardly flaring flange extendingfrom its central portion, the dial plate being seated on said flange andproviding a second bearing at its center for said spindle, and saidflange and dial plate having interlocking lugs and notches held in tightfrictional engagement for securing the dial plate tothe case.

4. In a magnetic speedometer of the type which includes a shaft, anannular magnet carried thereby, speed-responsive means associatedtherewith including a non-magnetic drag cup whose annular wallencompasses the magnet, a field plate extending over the drag cup, adial plate, a spindle for the drag cup journaled in the dial plate, anda cover glass over the dial plate with a spacer interposed between them;a case for said elements comprising a shell having a central annularportion extending adjacent the magnet with a central web at one end ofsaid annular portion of the case, and a bearing for the shaft secured tosaid web, the case being of stepped formation including a first stepextending radially outward from the other end of said annular portionfor seating the field plate, and a second step extending farther outwardfor seating the dial plate, together with a bezel ring embracing thecover glass and said second step with the spacer"

